Comparison of development and larval growth of four venerid clams

The development and larval morphology of four venerid calms, Ruditapes philippinarum, Mactra veneriformis, Cyclina sinensis, and Meretrix lusoria, which cohabit the intertidal zone in western coastal Korea, were compared using laboratory culture techniques. At 87 μm, the fertilized eggs of C. sinensis and M. lusoria were the largest and at 53 μm, those of M. veneriformis were the smallest. D-shaped larvae of M. lusoriu were the largest and those of M. veneriformis were the smallest measuring at 135 μm and 89 μm, respectively. D-shaped larvae of R. philippinarum and M. lusoria had symmetrical shoulder angles and an elliptical ventral form, in contrast to the asymmetrical shoulder angles and round ventral forms of M. veneriformis and C. sinensis. In general, pediveliger larvae of all species in the study were yellow, but those of M. veneriforks and C sinenis were a more pronounced yellow. In between the early D-shaped and pediveliger stage, 7 and 17 d elapsed for M. lusonia and C. sinensis larvae, respectively. In the early larval stages for all species, the sheU length was longer than the height. However, shell length and height later became approximately the same size in all species except R. philippinarum, which exhibited a flat shape. These results indicate that for these four venerid clams, the different characteristics in larval growth and external morphology provide the evidence necessary for larval identification of natural seed production despite the fact that they spawn concurrently in the intertidal zone.